Wafers for use in the fabrication of semiconductor chips include silicon wafers, gallium arsenide wafers and similar wafers. Among others, silicon wafers are being widely used. For example, silicon wafers are produced by cutting a high-purity single-crystal silicon ingot into slices having a thickness of the order of 500 to 1000 .mu.m. In recent years, these wafers are tending to become thinner as the size of chips is reduced and the production scale of chips is enlarged. Moreover, the diameter of these wafers is passing from the conventional value of 3-4 inches to 5-8 inches.
Silicon wafers are inherently fragile. In addition, silicon wafers having integrated circuits formed in their surface are easily broken, even under the action of slight external forces, because of their surface roughness. This disadvantage constitutes a serious obstacle to post-processing operations such as back surface grinding.
As a method for preventing silicon wafers from being broken during surface grinding there has conventionally been employed the method in which, prior to surface grinding, silicon wafers are coated with paraffin, resist ink or the like so as to compensate for their surface roughness and to distribute properly the external forces exerted thereon. However, this method involves the step of drying and solidifying paraffin or the like after its application to a wafer surface and the step of washing off the paraffin or the like from the ground wafer with a solvent under the application of heat, thus requiring complicated operation. In addition, this prior art method is still unable to prevent wafer breakage in the grinding of wafers having a diameter of 5 inches or greater, which has constituted a serious obstacle to the enhancement of productivity. Moreover, the use of paraffin or the like involves the problem of contamination of wafer surfaces. Accordingly, it has been strongly desired to develop a method for the prevention of wafer breakage which can replace the application of paraffin or the like.
As a method for the prevention of wafer breakage which can replace the application of paraffin or the like, one in which a processing film having an adhesive layer is affixed to a wafer surface has been investigated. However, this method has been unable to prevent wafer breakage perfectly. Moreover, it has been found that, where such a processing film is used, airborne dust may adhere to the adhesive layer during the manufacture, transport or storage of the film. If this dust is transferred and attached to the wafer surface, deterioration of the semiconductor due to wafer corrosion or the like and, further, malfunction or other problems may result. In other words, where such a processing film is used, the dust attached to the wafer surface cannot be satisfactorily removed simply by cleaning the processed wafer in the conventional manner. Because of these problems, no practical method for preventing wafer breakage by use of a processing film has been developed as yet.